Electric discharge device



Deli- 1942- J. H. HU'I 'CHINGS ELECTRIC DISQHARGE DEVICE Filed April 1, 1941 OUTLET INLET Inventor: v John H. Hutchings,

His Attorney.

Patented Dec. 29, 1942 UNITED STATES lPATEN'i @FFICE ELECTRIC DISCHARGE DEVICE John H. Hutchings, Schenectady, N. Y., assignor to General Electric Company, a corporation of N ew, York 6 Claims.

The present invention relates to electric discharge devices of the type which employs a pooltype cathode, such as a cathode constituted of mercury.

It is a principal object of the invention to provide an improved form of envelope construction for mercury pool rectifiers and an improved arrangement for mounting and cooling such rectifiers. In this connection an important feature of the invention consists in fabricating the envelope of two rimmed, cup-shaped parts which are joined with their open ends in abutting relation to provide an elongated container having a centrally projecting flange. The construction thus obtained is not only highly advantageous from the standpoint of low manufacturing cost but also possesses'numerous advantages with respect to the ease with which it may be incorporated in a mounting assembly. In a particular embodiment the central flange provides an efiective seat or abutment for properly locating the tube in a cooling structure adapted to be clamped to the exterior surface of the tube envelope at a region between the envelope extremities.

The features which I desire to protect herein are pointed out with particularity in the appended claims. The invention itself, together with. further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the drawing in which Fig. 1 is a longitudinal sectional View of a discharge apparatus suitably embodying the invention, Fig. 2 is a section taken on line 2-2 of Fig. 1, and Fig. 3 is a partial sectional view illustrating a modified application of the invention.

Referring particularly to Fig. 1, there is shown a controllable rectifier in which the envelope is constituted of two'cup-shaped parts Ill and l l positioned with their open ends in opposed, faceto-fac'e relation. Each of these parts has an externally projecting flange or rim I3, l4 and the two rims are hermetically joined, for example, by welding. With this arrangement the resultant structure comprises a generally cylindrical container having a centrally projecting flange or abutment l5. After its assembly, the envelope may be evacuated through a small tubulation I6 provided in connection with the envelope part II, the tubulation being finally sealed off as shown.

Within the envelope and at its upper end there is provided an anode I1, this element being in the form of a graphite cylinder mounted on a rod-like conductor l8. A lead-in arrangement comprising a flanged metal cylinder [9, a glass sleeve 29 and metal cap 2| serves insulatingly to support the anode (i. e. through the conductor l8) from the cup-shaped envelope part ID. A flexible copper cable 23, sheathed at its extremity by a steel ferrule 24 is soldered into the outer end of the conductor 18 and serves as a means for conducting current to the anode.

The lower end of the envelope contains a pool 25 of cathode material, preferably mercury, and a make-alive electrode 27 consisting of a body of resistance material (e. g. boron carbide) having its tip portion immersed in the mercury. The mercury is in direct contact with the floor of the envelope part H and is confined to a shallow depression 29 which permits a relatively small quantity of mercury to be employed. Mercury is prevented from entering the exhaust tubulation iii, either during or after evacuation of the envelope, by a flanged eyelet 33 provided in abutment with the tubulation within the envelope.

In the use of the device, a discharge between the cathode and the anode I l is initiated by connecting the electrode is? to an appropriate source of control potential (not shown). This connection is made through a lead-in conductor 35 which extends into the envelope through a metal eyelet 32, the conductor being insulatingly supported from the eyelet by means of a body of glass 33. Outside the envelope the conductor 3! is provided with an enlarged terminal 34 which facilitates connection to a control circuit.

The operating characteristics of a device of the type described are determined in large part by the mercury vapor pressure developed within the device. In particular, if this pressure attains too high a value, the likelihood of arc-back even at relatively low currents and voltages is substantially increased. Accordingly, if it is desired to use the device in a high power circuit, it is necessary to provide some means for maintaining the vapor pressure ata low value. This has ordinarily been done in the past by providing external cooling means in direct heat exchanging relation with the cathode pool.

I have found that excellent results may be obtained by confining the cooling action to a relatively narrow zone surrounding the discharge path between the anode and cathode, letting the other parts of the device attain very high temperatures. This discovery, when utilized in connection with a construction such as that illustrated in Fig. 1, makes possible an especially advantageous arrangement of the device with respect to the cooling means employed.

In the arrangement illustrated there is provided a detachable cooling structure 38 which is removably clamped to the external surface of the envelope part II. As is best shown in Fig. 2, this structure comprises a massive metal block containing a serpentine duct 40 through which an appropriate cooling fluid may be circulated, inlet and outlet conduits 42 and 43 being provided for the purpose of connecting the cooling structure to a fluid supply source. For the purpose of improving the heat transfer coefficient between the tube surface and the cooling structure 38 the bottom half of the tube may be tin dipped or otherwise suitably preconditioned.

To facilitate introduction and removal of the envelope, the cooling structure is split at 45, thus dividing it into two relatively separable components 38a and 38b. The uncut side of the structure possesses enough flexibility to permit some relative motion of the parts 38a and 38b and to permit these parts to be separated or drawn together by means of a bolt 54 which passes through the part 38a and is threaded into the part 381).

In order to assure that the cooling structure contacts the envelope surface in the most effective region, the structure is provided with a series of studs 49 adapted to abut against the flange [4 when the envelope is inserted in the cooling structure. These studs provide a fixed spacing of the cooling structure from the flange and make it easy to obtain the proper location of the rectifier with respect to the structure. The structure as a whole may be mounted on a panel board as indicated at 44 and may further be provided with a terminal stud 53 for supplying cur rent to the cathode.

With an arrangement such as that'described. the main body of the envelope may be permitted to attain a high temperature, say 300 0., as long as the section in contact with the cooling structure is maintained below about 100 (the actual temperature depending, of course, upon the intended operating conidtions). This means that the cooling fluid is required to remove only a portion of the total heat generated in the tube since the remainder can be effectively dissipated by direct radiation from the high temperature surfaces of the uncooled tube parts. Furthermore, the invention permits the quick substitution of one discharge tube for another in the event of a tube failure inasmuch as all the water connections, together with the cathode current supply connection. are made by a single clamping operation. This means also that the cooling structure may be made art of the permanent eouipment of the installation. thus bein not subject to renewal in the event of tube failure. This latter feature is especially advantageous in connection with air-cooled arrangements which require the use of cooling radiators of considerable complexity and cost.

An alternative mode of application of the invention is shown in Fig. 3 in which the illustrated construction differs from that of Fig. 1 in that it utilizes cup-like envelope parts 60 and M which are of different diameters. In addition, the flanges 62 and 63 of these parts are joined to the opposite surfaces of an annular metal plate or ring 64 having a portion thereof projecting into the interior of the envelope so as to provide a centrally apertured transverse baffle. Such a baffle has been found helpful in permitting the operation of the device at high voltages or high temperatures since its presence apparently decreases the likelihood of arc-back.

The apparatus of Fig. 3 also includes an anode 6%, a cathode 67 which is contained in a suitable recess formed in the floor of the envelope part 6 l, and a make-alive electrode 63, these elements functioning cooperatively in the manner specifled in connection with Fig. 1. It will be understood that the apparatus is intended to be combined with a detachable cooling structure (not shown) corresponding in nature and function to the structure 38 of Fig. 1.

While the invention has been described by reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without departing from the invention. I, therefore, aim in the appended claims to cover all such equivalent variations as come within the true spirit and scope of the foregoing disclosure.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Electric discharge apparatus comprising an elongated metal envelope, an anode and a pool type cathode within the envelope at opposite ends thereof, and cooling means in contact with a restricted region of the lateral walls of the envelope which is between and axially displaced from both the said anode and cathode.

2. Electric discharge apparatus comprising a generally cylindrical metal envelope, an anode and a pool-type cathode within the envelope at opposite ends thereof, and a detachable cooling structure circumferentially engaging the envelope in a restricted region which is between and axially displaced from both the said anode and cathode.

3. Electric discharge apparatus comprising an elongated envelope constituted of two cupshaped metal parts, the open end of each part having an external flange and the two flanges being hermetically joined in abutting relation, a pool-type cathode within one end of the envelope and in contact with the cup-shaped part which forms that end, an anode within the other end of the envelope, and a detachable cooling structure externally engaging the lateral wall surface of the envelope part which contains the cathode, the position of said structure being accurately determined by abutment of an element of the structure with the flange pertaining to the cup-shaped part with which the structure is associated.

4. Electric discharge apparatus comprising an elongated envelope constituted of two cup-sha ed metal parts, the open end of each part having an external flange and the two flanges being hermetically joined in abutting relation. a pooltype cathode within one end of the envelope and in contact with the cup-shaped part which forms that end, an anode displaced from the cathode toward the other end of the envelope and a cooling structure having separable components detachably engaging the lateral wall surface of the envelope part which contains the cathode, the position of said structure bein determined by abutment thereof with the flange pertaining to the said part.

5. Electric discharge apparatus comprising an elongated envelope constituted of two flanged cup-shaped metal parts positioned with their openings in opposed relation, an annular metal plate sandwiched between and hermetically joined to the flanges of the said parts, said plate portion of the envelope, a pool type cathode within one end of the envelope and in contact with the cup-shaped part which forms that end, an anode Within the other end of the envelope, a detachable cooling structure externally engaging the lateral wall surface of the envelope part which contains the cathode, and spacing means interposed between the cooling structure and the said central flange for fixing the axial position of the cooling structure with respect to the envelope.

JOHN H. HUTCHINGS. 

